The S-Pol radar was developed at NCAR/ATD to replace the CP-2 radar which served the research community for nearly twenty years. The purpose of S-Pol is to provide a cost effective state-of-the-art polarimetric weather radar for world wide deployment.

S-Pol has several significant improvements compared with CP-2. Its container transportation method allows practical temporary deployments worldwide including remote and difficult geographic sites. Additionally, S-Pol uses a high performance modern transmitter, low sidelobe parabolic antenna with high isolation between horizontal and vertical channels, and a modern dual channel receiver. The NCAR-designed VME data system provides numerous computed variables.

S-Pol completed operational tests during the spring of 1996 and is available for routine field deployments through the usual NCAR/ATD channels.

The entire S-Pol radar including generators and operations control area is packaged into six 20 foot sea containers. These containers are of a standard size which can easily be handled in seaports. They also can be shipped overland or by air as necessary. Site preparation and restoration costs are minimized because the antenna support structure is made from the shipping containers themselves. Although typically a radome is not required, the existing CP-2 radome system could be used to enclose the entire radar in extreme environments. The pedestal will be able to sufficiently control the exposed antenna in a 50 MPH wind.

The transmitter is an ASR-9 based unit built by Westinghouse. It uses an air cooled klystron and produces a one megawatt, one microsecond pulse. The PRF can range from 325 to 1200 pulses per second. The transmit pulse is tapered and filtered for minimum RF interference. The 28 foot reflector is a high-compliance aluminum structure providing -30 dB first sidelobes and at least -35 dB integrated cross polar isolation.

Polarization switching will be done by an NCAR built mechanical switch which will provide 49 dB transmit isolation. For alternating H/V pulses, this isolation is comparable to a dual transmitter configuration. A separate receiver for each channel provides 40 dB receive isolation. Dual receivers are required for cross polar measurements and to enable the low channel dwell times of the mechanical switch.

Pulse pair and dual polarization processing is performed by a NCAR designed VME-based Integrated Radar Acquisition system (VIRAQ). The VIRAQ processor uses a dual range 90 dB digital IF system with multiple C44 DSP chips that are controlled by a 486 CPU host running DOS.